In the construction of the viaduct referred to in the publications listed above, tubular piles consisting of steel pipes were used that had tapered tips of reinforced concrete and that, after being driven were filled with concrete. Each tip had a length of steel pipe extending from its smaller, lower end through its larger end with a portion protruding centrally thereof to enable a pile-forming length of steel pipe to be welded thereto at the job site. A steel plate covered the smaller end of the tip and was welded to the steel pipe at that end and to the reinforcements of the concrete body.
Tubular piles of the corrugated type are widely used but these must be secured to a mandrel that can absorb, while being driven, hammer energy that would usually damage the pile if applied directly thereto. Such mandrels are expansible so that they may be inserted in or removed from the pile and in use they extend the full length of the piles and when expanded they so grip the piles that relative movement between them does not occur while being driven. In practice, the mandrels have boots at their earth entering ends and these are exposed at the corresponding ends of the piles. Desirably, the maximum gripping pressure applied by a mandrel is at the earth entering end of the pile secured thereto.
Tapered, reinforced concrete tips for tubular piles of corrugated tubing have also been successfully used. Such tips incorporated a length of corrugated tubing to provide a mandrel receiving socket within the concrete body with a portion protruding from the upper end of the tip to enable a wanted pile-forming length of like tubing to be welded thereto.